1. Field of the Invention
The present invention relates to a flange used for a base support (drum) of an electrophotographic photoconductor and, more particularly, to a flange made of synthetic resin, a flange processing device, and a method for processing a flange.
2. Description of the Related Art
In the electrophotographic photoconductor field for electrostatic image processing in electrostatic copiers, electrostatic printers, facsimiles, etc., a photoconductor drum is generally provided with a photosensitive layer at the uppermost surface and equipped with flanges in the openings formed at either ends of the photoconductor drum, and various types of units are arranged around it. While the photoconductor drum rotates, these units perform necessary or desired processes (e.g., selective exposure, development, image transfer, charge removal, and cleaning) on the photoconductor layer.
An electrophotographic photoconductor is fabricated by assembling together a cylindrical drum base support with a photosensitive layer that has been processed to a desired surface condition and centered flange members, i.e., the drum base support and flange members are separately manufactured and then assembled into a photoconductor.
As shown for instance in FIG. 14, a flange member 10 made of synthetic resin or the like includes a flange part (or drum bumping part) 2 and an insertion part (or drum engagement part) 1 to be inserted into the inside of a cylindrical photoconductor drum (base support) 20. The insertion part 1 protruding toward the movable side B is fitted to the inner side of the photoconductor drum 20 and serves to firmly fix the flange member 10 to the photoconductor drum 20, and the flange part 2 serves to fix the positional relationship between the photoconductor drum 20 and flange member 10 by being bumped into the edge of the photoconductor drum 10. The outer surface of the flange part 2 is provided with a helical gear 3 (hereinafter simply referred to as a “gear part” in some cases) that is engaged with a drive gear (not shown) for transmitting rotational power to the helical gear 3. In addition, a shaft hole 4 is formed at the axial center of the flange member 10 so that the flange member is rotatively supported from the fixed side A. P/L denotes a reference plane. FIG. 15 is a cross-section of an example of a gear-equipped flange member of different shape, cut along a plane passing through its central axis. This flange member 10 has a protruding helical gear 3 at the fixed side A of a thin flange part 2, which the helical gear 3 is smaller in diameter than the flange part 2. A concentric shaft hole 4 is formed penetrating through the insertion part (drum engagement part) 1, flange part 2, and helical gear 3.
In a case where a flange member to be pressed into a photoconductor drum is made of resin, in the prior art, the flange member is provided with an insertion part (drum engagement part) and an insertion stopping part (e.g., a flange part at which the flange member is bumped into the drum). The shape of the flange member needs to be so designed that the area of the flange member contacting the drum is large enough to avoid the situation where only the flange member rotates when force has been applied for rotating the photoconductor drum. Accordingly, the outer surface of the drum engagement part of the flange member, contacting the photoconductor drum, is designed to conform to the surface of the photoconductor drum.
Flanges of this type for photoconductor drum are disclosed for instance in Japanese Patent Application Laid-Open (JP-A) Nos. 07-13468 and 10-319782. Moreover, electrophotographic photoconductors formed using flanges are disclosed for instance in JP-A Nos. 2003-233271, 2003-241573, 2003-255759 and 2004-184452.
An image forming apparatus is generally equipped with a development device for supplying a toner-containing developer to the photoconductor drum, or a latent image bearing member, in order to visualize a latent image on the drum. Such development device systems are widely used wherein a development roller carries brush-shaped toner-containing developer particles on its surface, which are then allowed to contact a latent image on the photoconductor for visualizing the latent image.
Meanwhile, for example, in a case of a magnetic developer, a known configuration of a development roller that carries brush-shaped developer particles on its surface is that multiple magnets that serve as main magnetic poles and transfer magnetic poles are arranged in the development roller, whereby developer particles that have been transferred on the roller surface by means of the transfer magnetic poles are agglomerated into sets of particles stacked on top of each other on the roller surface by the main magnetic poles, making them in contact with the photoconductor surface.
Because the height of the stack of the particles attached to the development roller is influenced by magnetic attraction, the distance between the development roller and the photoconductor, i.e., the so-called development gap, needs to be specified for optimized conditions in which the developer is supplied to and is in contact with the photoconductor surface (see for example JP-A No. 2004-184452 for more details in this regard).
Support and rotation of the photoconductor drum are generally provided by a rotation spindle or bearings that are provided to flanges attached to both ends of the photoconductor drum, or by power supplied via gears. For this reason, these flanges need to be precisely and firmly fitted into openings at both ends of the photoconductor drum. For smooth and precise rotation of the photoconductor drum, the centers of the flanges need to be constantly held at the axis of rotation.
In order to obtain high-resolution images in an electrophotographic apparatus equipped with a photoconductor by optimizing the foregoing conditions by specifying the development distance, it is effective to manufacture a high-precision photoconductor. More specifically, it is necessary to reduce radial run-out of the photoconductor drum with respect to the flanges attached to both ends of the drum. To achieve this, it is necessary to use high-precision flanges.
However, attachment of flanges to a photoconductor is often conducted by press-fitting in combination with an additive where necessary, and thus the concentricity of the center holes of the flanges relative to the photoconductor drum surface is dependent on the manner in which they were press-fitted into the photoconductor. In this case, because of surface deviations of the press-fitted portions of the flange members from their center holes as well as of deformation of the flanges as a result of press-fitting, it has been difficult to improve concentricity of the flange center holes relative to the photoconductor drum surface.
Flanges formed by injection molding of plastic have been generally used as conventional flanges for photoconductor drum. However, there have been limitations with respect to precision in parameters of these flanges due to a variety of factors including dimensional precision of the mold used, deterioration of the mold, reproducibility of assembling the mold after disassembled for cleaning, lot-to-lot variations of resin, and molding variations. Specific characteristic values are concentricity and roundness. For continued mass production of flanges, however, there is a limitation in these values—it is required to admit a concentricity of 15 μm between the center shaft hole and drum engagement part of the flange and a roundness of 10 μm for both the shaft hole and drum engagement part. As described above, however, it is imperative to provide high-precision flanges for high-precision image formation. To achieve this, it is necessary that the molded article be subjected to a second cutting process to produce a high-precision component. Known technologies (methods and system) undesirably require a lot of skill and many steps for this.
Moreover, flanges for photoconductor drum are often equipped with a gear for transmitting driving force. In this case the mesh precision of the gear is an important characteristic value. Because of the structure of the mold, it has been difficult for flanges for photoconductor drum that are formed by injection molding to simultaneously exhibit high gear precision and high concentricity of the shaft hole relative to the drum engagement part diameter (see FIG. 15).